PPC: [turbofan] Load immortal heap objects from the heap roots.

PPC: [turbofan] Load immortal heap objects from the heap roots.

Port 5d2de78a771b8ff1ac59fbdf634bffd01709b554

Original commit message:
It's cheaper to materialize heap constants by loading from the roots
array instead of embedding the constant into the instruction stream, at
least on x64, arm and arm64.

Drive-by-fix: Also cleanup the materialize constant from frame
optimization.

R=michael_dawson@ca.ibm.com
BUG=

Committed: https://crrev.com/8ad33d6db6de581c71a9668158910eaaccdce1dd
Cr-Commit-Position: refs/heads/master@{#27823}

[MTBrandyberry, 2015-04-14 14:36:14]

Port optimization to PPC.

[MTBrandyberry, 2015-04-14 14:39:18]

mbrandy@us.ibm.com changed reviewers:
+ dstence@us.ibm.com

[MTBrandyberry, 2015-04-14 14:41:50]

mbrandy@us.ibm.com changed reviewers:
+ joransiu@ca.ibm.com

[michael_dawson, 2015-04-14 14:51:14]

On 2015/04/14 14:36:14, mtbrandyberry wrote:
> Port optimization to PPC.

lgtm.

[MTBrandyberry, 2015-04-14 14:53:10]

The CQ bit was checked by mbrandy@us.ibm.com

[commit-bot: I haz the power, 2015-04-14 14:53:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1075303003/1

[commit-bot: I haz the power, 2015-04-14 15:17:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-14 15:17:47]

Patchset 1 (id:??) landed as
https://crrev.com/8ad33d6db6de581c71a9668158910eaaccdce1dd
Cr-Commit-Position: refs/heads/master@{#27823}